Inhibition of interleukin-6 attenuates erectile dysfunction in a rat model of nerve-sparing radical prostatectomy

IntroductionThe precise mechanisms underlying erectile dysfunction (ED) occurring after cavernous nerve (CN)‐sparing surgery remain to be determined.AimTo evaluate the expression of interleukin‐6 (IL‐6) and IL‐6 receptor (IL‐6R) after CN injury, and the effect of inhibiting IL‐6 bioactivity on nerve injury‐related ED.MethodsMale Sprague‐Dawley rats were divided into three groups: sham operation; bilateral CN dissection without crushing or cutting; and bilateral CN resection. In the interventional experiment, male rats underwent bilateral CN dissection, and anti‐rat IL‐6 antibody in phosphate‐buffered saline (PBS) or vehicle alone was injected intraperitoneally immediately and 24 hours after CN dissection.Main Outcome MeasuresOne, 3, 7, 28, and 56 days after surgery, the expression of IL‐6 and IL‐6R in the major pelvic ganglion (MPG) was examined by real‐time polymerase chain reaction. In the interventional experiment, erectile function was assessed by determining intracavernous pressure divided by arterial pressure (ICP/AP) during electrical pelvic nerve stimulation at 4 weeks after surgery in the anti‐IL‐6‐injected rats and PBS‐injected rats. The degree of nerve injury was also evaluated by retrograde dye tracing with Fluorogold.ResultsThe expression levels of IL‐6 and IL‐6R were increased in the early period of CN injury, as compared with the sham group. IL‐6 expression on day 1 was particularly enhanced. Four weeks after CN dissection, the anti‐IL‐6 group had greater ICP/AP and more FG‐positive cells than the PBS group.ConclusionsExpression levels of IL‐6 in the MPG were increased in the acute phase following CN injury. Inhibition of IL‐6 bioactivity attenuated ED following CN dissection. Thus, the suppression of excess inflammatory responses in the acute phase may lead to improvements in ED occurring after nerve‐sparing radical prostatectomy. Yamashita S, Kato R, Kobayashi K, Hisasue S, Arai Y, and Tsukamoto T. Inhibition of interleukin‐6 attenuates erectile dysfunction in a rat model of nerve‐sparing radical prostatectomy. J Sex Med 2011;8:1957–1964.     

The Neuroprotective Effect of Platelet‐rich Plasma on Erectile Function in Bilateral Cavernous Nerve Injury Rat Model

IntroductionNeurogenic erectile dysfunction resulting from cavernous nerve (CN) injury is a major complication caused by radical prostatectomy. The use of platelet‐rich plasma (PRP) on the nerve‐injured site has shown promising results for the nerve regeneration. However, the effects of PRP injection in corpus cavernosum after bilateral CN injury have never been investigated.AimTo assess the neuroprotective effect of PRP injection in corpus cavernosum after bilateral CN injury.MethodsMale Sprague‐Dawley rats were randomly divided into three groups: Group I underwent sham operation, while the remaining two groups underwent bilateral CN crush. Crush injury groups were treated at the time of injury with an application of PRP or normal saline only injection in the corpus cavernosum, respectively. Four weeks later, erectile function (EF) was assessed by CN electrosimulation, and CNs as well as penile tissue were collected for histology.Main Outcome MeasuresIntracavernous pressure (ICP) monitored during electrical stimulation of CNs; myelinated axons number of CNs and dorsal penile nerve; collagen type change, number of apoptotic cells, and mRNA expression of caspase‐3 and transforming growth factor‐β1 (TGF‐β1) in the corpus cavernosum.ResultsFour weeks after surgery, in the vehicle‐only group, the functional evaluation showed a lower mean maximal ICP than that in the sham group (P < 0.05). PRP treatments resulted in significant recovery of EF, as compared with the vehicle‐only group (P < 0.05). Histologically, the PRP‐treated group had a significant preservation of myelinated axons of CNs compared with the vehicle‐only group (P < 0.05) and reduced the apoptotic index. The mRNA expression of TGF‐β1 in the corpus cavernosum tissue was significantly decreased in the PRP group compared with the vehicle‐only group (P < 0.05).ConclusionsPRP injection in the corpus cavernosum increased the number of myelinated axons and facilitated recovery of EF in the bilateral CN injury rat model. Wu C‐C, Wu Y‐N, Ho H‐O, Chen K‐C, Sheu M‐T, and Chiang H‐S. The neuroprotective effect of platelet‐rich plasma on erectile function in bilateral cavernous nerve injury rat model. J Sex Med 2012;9:2838–2848.     

GGF2 Is Neuroprotective in a Rat Model of Cavernous Nerve Injury-Induced Erectile Dysfunction

IntroductionErectile dysfunction is a major complication of radical prostatectomy, commonly associated with penile neuropathy. In animal models of peripheral nerve injury, glial growth factor-2 (GGF2), a member of the neuregulin family of growth factors, has neuroprotective and neurorestorative properties, but this potential has not been established after cavernous nerve (CN) injury.AimsThe effectiveness of GGF2 in preserving axonal integrity and recovering erectile function in a rat model of radical prostatectomy-associated CN injury.MethodsAdult male Sprague-Dawley rats underwent bilateral CN crush injury (BCNI) or sham surgery. Rats were administered GGF2 (0.5, 5, or 15 mg/kg) or vehicle subcutaneously 24 hour pre and 24-hour post-BCNI, and once weekly for 5 weeks. Erectile function was assessed in response to electrical stimulation of the CN. CN survival was assessed by fluorogold retrograde axonal tracing in major pelvic ganglia (MPG). Unmyelinated axons in the CNs were quantitated by electron microscopy.Main Outcome MeasuresErectile function recovery, CN survival, and unmyelinated CN axon preservation in response to GGF2 treatment following BCNI.ResultsErectile function was decreased (P < 0.05) after BCNI, and it was improved (P < 0.05) by all doses of GGF2. The number of fluorogold-labeled cells in the MPG was reduced (P < 0.05) by BCNI and was increased (P < 0.05) by GGF2 (0.5 and 5 mg/kg). The percentage of denervated Schwann cells in the BCNI group was higher (P < 0.05) than that in the sham-treated group and was decreased (P < 0.05) in the GGF2-treated (5 mg/kg) BCNI group. In the BCNI + GGF2 (5 mg/kg) group, the unmyelinated fiber histogram demonstrated a rightward shift, indicating an increased number of unmyelinated axons per Schwann cell compared with the BCNI group.ConclusionsGGF2 promotes erectile function recovery following CN injury in conjunction with preserving unmyelinated CN fibers. Our findings suggest the clinical opportunity to develop GGF2 as a neuroprotective therapy for radical prostatectomy. Burnett AL, Sezen SF, Hoke A, Caggiano AO, Iaci J, Lagoda G, Musicki B, and Bella AJ. GGF2 is neuroprotective in a rat model of cavernous nerve injury-induced erectile dysfunction. J Sex Med 2015;12:897–905.     

Increased Expression of the Neuroregenerative Peptide Galanin in the Major Pelvic Ganglion Following Cavernous Nerve Injury

IntroductionErectile dysfunction (ED) remains a frequent complication of radical prostatectomy due to injury to the cavernous nerves (CNs). A recent microarray showed the neuropeptide galanin to be one of the most strikingly upregulated genes in the rat major pelvic ganglion (MPG) after bilateral CN crush injury (BCNI).AimThe aim of this study is to evaluate the temporal regulation of galanin in the MPG after BCNI and its relationship to functional nerve regeneration.MethodsChanges in galanin, galanin receptor (galR), and c‐JUN mRNA expression were assessed in Sprague‐Dawley rats after sham operation (n = 10) and at 48 hours (n = 10), 7 (n = 10), 14 (n = 5), 21 (n = 5), 30 (n = 5), and 60 (n = 5) days after BCNI using quantitative PCR. Erectile function was assessed by measuring intracavernous pressure (ICP) divided by mean arterial pressure (MAP) during CN electrostimulation. Immunohistochemistry was performed on the MPG in sham‐operated animals and 5 days after BCNI.Main Outcome MeasuresICP/MAP upon CN stimulation; galanin, galR1, ‐2, ‐3, and c‐JUN mRNA expression at various time points after BCNI; and nNOS, galanin, and galR distribution in the MPG of sham‐operated rats and after BCNI.ResultsAfter BCNI, ICP/MAP values quickly deteriorate, while after 60 days, spontaneous restoration of erectile responses to CN stimulation is observed, reflecting CN regeneration. Galanin mRNA in the MPG is up to 186‐fold upregulated compared with sham‐operated rats at 48 hours and 7 days after BCNI and gradually declines with increasing time from injury, whereas galanin receptor expressions decrease and c‐JUN gradually increases. Galanin expression shows a strong inverse correlation with erectile responses to CN stimulation with time from injury. Injured MPGs show a colocalization between galanin‐ and nNOS‐positive neuronal cell population in the MPG.ConclusionsGalanin is upregulated in the MPG in the early phase after CN injury after which it gradually decreases and is present in nNOS‐positive neurons of the ganglion. We hypothesize that galanin upregulation is an important factor in the endogenous neuroregenerative response to CN injury. Weyne E, Albersen M, Hannan JL, Castiglione F, Hedlund P, Verbist G, De Ridder D, Bivalacqua TJ, and Van der Aa F. Increased expression of the neuroregenerative peptide galanin in the major pelvic ganglion following cavernous nerve injury. J Sex Med 2014;11:1685–1693.     

Effects of Intravenous Injection of Adipose‐Derived Stem Cells in a Rat Model of Radiation Therapy‐Induced Erectile Dysfunction

IntroductionRadiation therapy (RT) for prostate cancer is frequently associated with posttreatment erectile dysfunction (ED).AimTo investigate whether injection of adipose‐derived stem cells (ADSCs) can ameliorate RT‐associated ED.MethodsThirty male rats were divided into three groups. The control + phosphate‐buffered saline (PBS) group received tail‐vein injection of PBS. The radiation + PBS group received radiation over the prostate and tail‐vein injection of PBS. The radiation + ADSC group received radiation over the prostate and tail‐vein injection of ADSCs, which were labeled with 5‐ethynyl‐2‐deoxyuridine (EdU). Seventeen weeks later, erectile function was evaluated by intracavernous pressure (ICP) in response to electrostimulation of cavernous nerves (CNs). Penile tissue and major pelvic ganglia (MPG) were examined by immunofluorescence (IF) and EdU staining.Main Outcome MeasuresErectile function was measured by ICP. Protein expression was examined by IF, followed by image analysis and quantification.ResultsRadiation over the prostate caused a significant decrease in erectile function and in the expression of neuronal nitric oxide synthase (nNOS) in penis and MPG. Cavernous smooth muscle (CSM) but not endothelial content was also reduced. Injection of ADSCs significantly restored erectile function, nNOS expression, and CSM content in the irradiated rats. EdU‐positive cells were visible in MPG.ConclusionsRadiation appears to cause ED via CN injury. ADSC injection can restore erectile function via CN regeneration. Qiu X, Villalta J, Ferretti L, Fandel TM, Albersen M, Lin G, Dai Y, Lue TF, and Lin C‐S. Effects of intravenous injection of adipose‐derived stem cells in a rat model of radiation therapy‐induced erectile dysfunction. J Sex Med 2012;9:1851–1858.     

Oral l‐Citrulline Supplementation Improves Erectile Function in Rats with Acute Arteriogenic Erectile Dysfunction

IntroductionOral l‐citrulline supplementation increases serum l‐arginine levels more efficiently than l‐arginine itself and increases nitric oxide (NO) production.AimTo investigate whether oral l‐citrulline supplementation improves erectile function in rats with acute arteriogenic erectile dysfunction (ED).MethodsWe divided 8‐week‐old male Wistar‐ST rats into 3 groups: sham‐operated rats (control group), arteriogenic ED rats who underwent ligation of both internal iliac arteries (ligation group), and arteriogenic ED rats receiving oral 2% l‐citrulline water supplementation (citrulline group). Citrulline water was given to arteriogenic ED rats for 3 weeks from 1 week after surgery. Erectile function was evaluated by maximum intracavernous pressure/mean arterial pressure (ICP/MAP) ratios via cavernous nerve stimulation at 4 weeks after surgery. Then, the penises were resected, stained with Masson's trichrome, and observed microscopically. Serum nitrogen oxides (NOx) levels were measured by high‐performance liquid chromatography. Bonferroni's multiple t‐test was used for statistical analysis.Main Outcome MeasuresThe main outcome measures were changes in ICP/MAP, smooth muscle (SM)/collagen ratios, and NOx levels following l‐citrulline supplementation.ResultsThe ICP/MAP ratio in the ligation group was significantly lower than that in the control group (P < 0.05), denoting ED. The ICP/MAP ratio of the citrulline group was significantly higher than that of the ligation group (P < 0.05), indicating ED amelioration. Levels of NOx in the ligation group were significantly lower than in the control group (P < 0.05), while those in the citrulline group were significantly higher than in the ligation group (P < 0.05). SM/collagen ratios in the ligation group were significantly lower than in the control group (P < 0.05), while ratios in the citrulline group were significantly higher than those in the ligation group (P < 0.05).ConclusionsOral l‐citrulline supplementation improved ICP/MAP and SM/collagen ratios and increased NOx. Therefore, oral l‐citrulline supplementation might be a useful novel therapy for acute arteriogenic ED. Shiota A, Hotta Y, Kataoka T, Morita M, Maeda Y, and Kimura K. Oral l‐citrulline supplementation improves erectile function in rats with acute arteriogenic erectile dysfunction. J Sex Med 2013;10:2423–2429.     

Low-Intensity Electrostimulation Enhances Neuroregeneration and Improves Erectile Function in a Rat Model of Cavernous Nerve Injury

BackgroundNeurogenic erectile dysfunction (ED) following radical prostatectomy (RP) is a frequent complication often leading to erectile tissue remodeling and permanent ED. Low-intensity electrostimulation (LIES) has been shown to enhance peripheral nerve regeneration, however, its application on cavernous nerves (CN) has never been investigated.AimsTo investigate whether LIES enhances CN regeneration, improves erectile function (EF) recovery, and prevents corpora cavernosal remodeling after CN injury, which is a principal factor for ED following RP.MethodsAdult male Sprague-Dawley rats were divided into Sham, Bilateral Cavernous Nerve Injury (BCNI), and BCNI + LIES (1V, 0.1ms, 12Hz, 1h/day). After 7days, EF was assessed (ICP measurement). Penes and CN were collected for molecular analyses of TGF-$\beta$1, Il-6, CRP, eNOS, ERK and AKT protein levels in corpus cavernosum (CC), and immunohistological analysis of DHE, total collagen and α-SMA in CC and S-100, Tub-III, DAPI, TUNEL, and nNOS in CN.OutcomesEffects of LIES on EF, erectile tissue remodeling and CN structure.ResultsEF was decreased (P < .05) 7 days after BCNI and increased (P < .05) by LIES. Intracavernosal reactive oxygen species (DHE) was increased (P < .05) after BCNI and normalized by LIES. Protein expressions of TGF-β1, IL-6, and CRP were increased in the penis (P < .05) after BCNI and normalized by LIES. The α-SMA and/or total collagen ratio was decreased (P < .05) after BCNI in the penis and normalized by LIES. Protein expression ratio of p-ERK/ERK and p-AKT/AKT did not change after BCNI but increased (P < .05) in LIES group. Myelination and number of nNOS positive cells in the CN were decreased (P < .05) after BCNI and normalized by LIES. The number of apoptotic nerve cells within the dorsal penile nerve was increased (P < .05) after BCNI and decreased (P < .05) by LIES compared to the BCNI group. There were no differences in eNOS expression in the penis between study groups.Clinical TranslationLIES may offer a potential new tool for penile rehabilitation and ED management following RP, potentially enhancing EF recovery and minimizing the side effects of this surgery.Strengths & LimitationsThis study provides evidence of the protective effect of LIES on EF and tissue remodeling following CN injury; nevertheless, this study has been conducted on animals and the translation to humans remains to be demonstrated. Further research to identify the underlying mechanisms of action is required.ConclusionThis study demonstrates that LIES of the CN after CN injury protects CN structure, enhances EF recovery, and prevents corpora cavernosal remodeling.Sturny M, Karakus S, Fraga-Silva R, et al. Low-Intensity Electrostimulation Enhances Neuroregeneration and Improves Erectile Function in a Rat Model of Cavernous Nerve Injury. J Sex Med 2022;19:686–696.     

Incomplete Recovery of Erectile Function in Rat after Discontinuation of Dual 5‐Alpha Reductase Inhibitor Therapy

AimThe association of 5‐alpha reductase inhibitor (5ARI) therapy and sexual dysfunction has been reported. Some patients claim persistent erectile dysfunction despite long‐term discontinuation of 5ARI treatment. The aim of this study was to assess erectile function after cessation of 5ARI therapy using a rat model.MethodsTwenty‐six adult male Sprague‐Dawley rats were randomized into three groups: (i) control (N = 10); (ii) 8‐week dutasteride treatment (0.5 mg/rat/day, in drinking water, N = 8); and (iii) 6‐week dutasteride treatment followed by a 2‐week washout period (N = 8). The experiments were performed after 8 weeks from the initiation of treatment in all groups. In vivo erectile activity and in vitro contractile and relaxant responses of cavernosal smooth muscle were investigated.ResultsIn vivo erectile activity (intracavernosal pressure [ICP]/mean arterial pressure [MAP] and total ICP) in treatment groups were significantly decreased compared with controls (ICP/MAP: P < 0.001 for 2.5 v, 5 v, and 7.5 v; total ICP: P < 0.001 for 5 v and P < 0.01 for 7.5 v). Acetylcholine‐induced relaxations were diminished in treatment groups (P < 0.05). Relaxant responses to electrical field stimulation (EFS) were decreased in the 8‐week treatment group (P < 0.05) but were similar to controls in the washout group. Sodium nitroprusside (SNP)‐induced endothelium‐independent relaxations were reduced in the 8‐week dutasteride treatment group (P < 0.01), while these responses were restored in the washout group. The contractile responses to the alpha1‐adrenergic agonist phenylephrine were decreased in treatment groups compared with controls (P < 0.01). Direct neurogenic contractile responses in the dutasteride groups were significantly lower than controls between 1 and 15 Hz frequencies (but not at 20 Hz) and washout partially restored the responses at 10 and 15 Hz.ConclusionDiscontinuation of dutasteride improved the relaxant responses to EFS and SNP, while cholinergic and adrenergic responses remained depressed. Our findings suggest a time‐dependent detriment of dutasteride on erectile function. The withdrawal/washout effect of 5ARIs on parameters of human sexual function warrants further investigation. Öztekin ÇV, Gur S, Abdulkadir NA, Lokman U, Akdemir AÖ, Cetinkaya M, and Hellstrom WJG. Incomplete recovery of erectile function in rat after discontinuation of dual 5‐alpha reductase inhibitor therapy. J Sex Med 2012;9:1790–1798.     

Hydroxyl Fasudil,an Inhibitor of Rho Signaling,Improves Erectile Function in Diabetic Rats: A Role for Neuronal ROCK

IntroductionThe pathogenesis of diabetic erectile dysfunction (ED) includes neuropathy, but the molecular basis for neurogenic ED is incompletely understood. The RhoA/ROCK pathway has been implicated in diabetic neuropathy and in ED, but its role in diabetic neurogenic ED is not known.AimsThe aim of this study was to determine whether hydroxyl fasudil, a ROCK inhibitor, affects diabetic neuropathy‐related ED.MethodsType 1 diabetes mellitus was induced in male rats by streptozotocin (75 mg/kg, intraperitoneally). After 8 weeks, diabetic rats were administered hydroxyl fasudil, a selective ROCK inhibitor (10 mg/kg/day, intraperitoneally) or vehicle, for 4 weeks. Age‐matched control, nondiabetic, rats were treated intraperitoneally for 4 weeks with saline. At week 12, after a 2 day washout, neuro‐stimulated erectile function was evaluated. Major pelvic ganglia (MPG) were collected for Western blot analysis of RhoA, ROCK‐1, ROCK‐2, phospho (P)‐AKT (Ser⁴⁷³), and P‐phosphatase and tensin homolog (P‐PTEN) (Ser³⁸⁰/Thr^382/383).Main Outcome MeasuresEffect of ROCK inhibitor hydroxyl fasudil on erectile function and ROCK/P‐AKT/P‐PTEN pathway in the MPG of diabetic rats.ResultsErectile response was significantly (P < 0.05) reduced in diabetic rats compared with nondiabetic rats and was preserved (P < 0.05) in diabetic rats treated with hydroxyl fasudil. In diabetic rats, RhoA and ROCK‐2 protein expressions in MPG were increased (P < 0.05) and remained increased in hydroxyl fasudil‐treated rats. P‐AKT (Ser⁴⁷³) expression was decreased (P < 0.05), whereas P‐PTEN (Ser³⁸⁰/Thr^382/383) expression was increased (P < 0.05) in MPG of diabetic rats compared with nondiabetic rats, and both were reversed (P < 0.05) in diabetic rats treated with hydroxyl fasudil.ConclusionImproved erectile function and restored P‐AKT and P‐PTEN in the MPG with hydroxyl fasudil treatment suggest the role of Rho signaling via PTEN/AKT pathway in neurogenic diabetic ED. Sezen SF, Lagoda G, Musicki B, and Burnett AL. Hydroxyl fasudil, an inhibitor of Rho signaling, improves erectile function in diabetic rats: A role for neuronal ROCK. J Sex Med 2014;11:2164‐2171.     

Insulin-Like Growth Factor-1–Loaded Polymeric Poly(Lactic-Co-Glycolic) Acid Microspheres Improved Erectile Function in a Rat Model of Bilateral Cavernous Nerve Injury

Background

Previous studies have documented improvement in erectile function after bilateral cavernous nerve injury (BCNI) in rats with the use of pioglitazone. Our group determined this improvement to be mediated by the insulin-like growth factor-1 (IGF-1) pathway.

Valproic Acid Prevents Penile Fibrosis and Erectile Dysfunction in Cavernous Nerve‐Injured Rats

IntroductionBilateral cavernous nerve injury (BCNI) causes profound penile changes such as apoptosis and fibrosis leading to erectile dysfunction (ED). Histone deacetylase (HDAC) has been implicated in chronic fibrotic diseases.AimsThis study will characterize the molecular changes in penile HDAC after BCNI and determine if HDAC inhibition can prevent BCNI‐induced ED and penile fibrosis.MethodsFive groups of rats (8–10 weeks, n = 10/group) were utilized: (i) sham; (ii and iii) BCNI 14 and 30 days following injury; and (iv and v) BCNI treated with HDAC inhibitor valproic acid (VPA 250 mg/kg; 14 and 30 days). All groups underwent cavernous nerve stimulation (CNS) to determine intracavernosal pressure (ICP). Penile HDAC3, HDAC4, fibronectin, and transforming growth factor‐β1 (TGF‐β1) protein expression (Western blot) were assessed. Trichrome staining and the fractional area of fibrosis were determined in penes from each group. Cavernous smooth muscle content was assessed by immunofluorescence to alpha smooth muscle actin (α‐SMA) antibodies.Main Outcome MeasuresWe measured ICP; HDAC3, HDAC4, fibronectin, and TGF‐β1 protein expression; penile fibrosis; penile α‐SMA content.ResultsThere was a voltage‐dependent decline (P < 0.05) in ICP to CNS 14 and 30 days after BCNI. Penile HDAC3, HDAC4, and fibronectin were significantly increased (P < 0.05) 14 days after BCNI. There was a slight increase in TGF‐β1 protein expression after BCNI. Histological analysis showed increased (P < 0.05) corporal fibrosis after BCNI at both time points. VPA treatment decreased (P < 0.05) penile HDAC3, HDAC4, and fibronectin protein expression as well as corporal fibrosis. There was no change in penile α‐SMA between all groups. Furthermore, VPA‐treated BCNI rats had improved erectile responses to CNS (P < 0.05).ConclusionHDAC‐induced pathological signaling in response to BCNI contributes to penile vascular dysfunction. Pharmacological inhibition of HDAC prevents penile fibrosis, normalizes fibronectin expression, and preserves erectile function. The HDAC pathway may represent a suitable target in preventing the progression of ED occurring post‐radical prostatectomy. Hannan JL, Kutlu O, Stopak BL, Liu X, Castiglione F, Hedlund P, Burnett AL, and Bivalacqua TJ. Valproic acid prevents penile fibrosis and erectile dysfunction in cavernous nerve‐injured rats. J Sex Med 2014;11:1442–1451.     

Nitric Oxide‐Releasing Polymeric Microspheres Improve Diabetes‐Related Erectile Dysfunction

IntroductionWe have used a long‐acting nitric oxide (NO)‐releasing polymer to develop injectable biodegradable microspheres capable of localized NO release over prolonged periods of time.AimThe aim of this study was to evaluate the therapeutic potential of these microspheres for diabetes‐related erectile dysfunction (ED) in the rat model.MethodsNO‐releasing microspheres were incubated in physiologic buffer, and in vitro NO release was measured using a Griess assay. To ensure no migration, microspheres were fluorescently tagged and injected into the corpus cavernosum of adult rats, and fluorescent imaging was performed weekly for 4 weeks, at which point rats were sacrificed. To assess physiologic efficacy, diabetes was induced in 40 rats using streptozotocin (STZ), whereas 10 rats were kept as age‐matched controls. Diabetic rats were divided into four groups: no treatment, sildenafil, NO‐releasing microspheres, and combination therapy. For each rat, the cavernosal nerve (CN) was stimulated at various voltages, and intracavernosal pressure (ICP) and mean arterial pressure (MAP) were measured via corpus cavernosum and carotid artery catheterization, respectively. Long‐term efficacy was determined by injecting diabetic rats with microspheres and measuring erectile response at predetermined intervals for up to 5 weeks.Main Outcome MeasuresErectile response was determined via calculation of mean peak ICP/MAP and area under curve (AUC) for each experimental group.ResultsUnder physiologic conditions in vitro, microspheres continued NO release for up to 4 weeks. Fluorescent imaging revealed no detectable signal in tissues besides cavernosal tissue at 4 weeks postinjection. Upon CN stimulation, peak ICP/MAP ratio and AUC of diabetic rats improved significantly (P < 0.05) in microsphere and combination therapy groups compared with no treatment and sildenafil groups. In long‐term efficacy studies, microspheres augmented the effect of sildenafil for 3 weeks following injection (P < 0.05).ConclusionsNO‐releasing microspheres significantly improved erectile response in diabetic rats for 3 weeks and hence offer a promising approach to ED therapy, either as monotherapy or combination therapy. Soni SD, Song W, West JL, and Khera M. Nitric oxide‐releasing polymeric microspheres improve diabetes‐related erectile dysfunction. J Sex Med 2013;10:1915‐1925.     

FK506 neuroprotection after cavernous nerve injury is mediated by thioredoxin and glutathione redox systems

IntroductionImmunophilin ligands such as FK506 (FK) preserve erectile function (EF) following cavernous nerve injury (CNI), although the precise mechanisms are unclear. We examined whether the thioredoxin (Trx) and glutathione (GSH) redox systems mediate this effect after CNI.AimTo investigate the roles of Trx reductase 2 (TrxR2) and S‐Nitrosoglutathione reductase (GSNOR) as antioxidative/nitrosative and antiapoptotic mediators of the neuroprotective effect of FK in the penis after CNI.MethodsAdult male rats, wild‐type (WT) mice, and GSNOR deficient (GSNOR ‐/‐) mice were divided into four groups: sham surgery (CN [cavernous nerves] exposure only) + vehicle; sham surgery + FK (5 mg/kg/day/rat or 2 mg/kg/day/mouse, for 2 days, subcutaneous); CNI + vehicle; and CNI + FK. At day 4 after injury, electrically stimulated changes in intracavernosal pressure (ICP) were measured. Penises were collected for Western blot analysis of TrxR2, GSNOR, and Bcl‐2, and for immunolocalization of TrxR2 and GSNOR.Main Outcome MeasuresEF assessment represented by maximal ICP and total ICP in response to electrical stimulation. Evaluation of protein expression levels and distribution patterns of antioxidative/nitrosative and antiapoptotic factors in penile tissue.ResultsEF decreased after CNI compared with sham surgery values in both rats (P < 0.01) and WT and GSNOR ‐/‐ mice (P < 0.05). FK treatment preserved EF after CNI compared with vehicle treatment in rats (P < 0.01) and WT mice (P < 0.05) but not in GSNOR ‐/‐ mice. In rats, GSNOR (P < 0.01) and Bcl‐2 (P < 0.05) expressions were significantly decreased after CNI. FK treatment in CN‐injured rats restored expression of GSNOR and upregulated TrxR2 (P < 0.001) and Bcl‐2 (P < 0.001) expressions compared with vehicle treatment. Localizations of proteins in the penis were observed for TrxR2 (endothelium, smooth muscle) and for GSNOR (nerves, endothelium, smooth muscle).ConclusionsThe neuroprotective effect of FK in preserving EF after CNI involves antioxidative/nitrosative and antiapoptotic mechanisms mediated, to some extent, by Trx and GSH systems. Lagoda G, Xie Y, Sezen SF, Hurt KJ, Liu L, Musicki B, and Burnett AL. FK506 neuroprotection after cavernous nerve injury is mediated by thioredoxin and glutathione redox systems. J Sex Med **;**:**–**.     

Involvement of Rho‐Kinase/LIM Kinase/Cofilin Signaling Pathway in Corporal Fibrosis after Cavernous Nerve Injury in Male Rats

IntroductionThe molecular mechanism of corporal fibrosis leading to erectile dysfunction (ED) following cavernous nerve (CN) injury is poorly understood.AimTo determine whether the LIMK2/cofilin pathway, the downstream effectors of ROCK1, was involved in ED and corporal fibrosis following bilateral CN injury in male rats.MethodsForty‐eight 10‐week‐old male Sprague‐Dawley rats were equally divided into three groups: sham surgery (S); bilateral CN crush injury (I); and bilateral CN resection (R). Within each groups, two subgroups were analyzed at 1 and 4 weeks postoperatively.Main Outcome MeasuresElectrostimulation was performed to assess erectile function by the ratio of maximal intracavernous pressure to mean arterial pressure (ICP/MAP) and areas under the ICP curve to MAP (AUC/MAP). Penile tissue was processed for Masson's trichrome staining, Western blot (ROCK1, total LIMK2, phospho‐LIMK2, total cofilin, phospho‐cofilin), immunohistochemistry (alpha‐SM actin [α‐SMA]), and double immunofluorescent staining (ROCK1, phospho‐LIMK2, vimentin).ResultsAt each time point, both I and R groups showed a significantly lower percent of ICP/MAP and AUC, and decreased SM cell/collagen ratio and expression of α‐SMA than S group. Densitometry revealed a significantly higher expression of ROCK1 in I and R groups compared with S group at all time points. The LIMK2 phosphorylation in I and R groups significantly increased at 1 week, but not at 4 weeks. The cofilin phosphorylation in R group significantly increased to that in S group starting at 1 week, while that in I group was increased significantly at 4 weeks. The double immunofluorescent staining noted that coexpression of vimentin with ROCK1 or phospho‐LIMK2 in I and R groups was significantly increased mainly in the subtunical area at 1 week but not at 4 weeks.ConclusionsThe ROCK1/LIMK2/cofilin pathway may be involved in ED related to corporal fibrosis, and it appears to be functional particularly in the early period after CN injury. Song SH, Park K, Kim SW, Paick J‐S, and Cho MC. Involvement of Rho‐kinase/LIM kinase/cofilin signaling pathway in corporal fibrosis after cavernous nerve injury in male rats. J Sex Med 2015;12:1522–1532.     

Chronic vardenafil treatment improves erectile function via structural maintenance of penile corpora cavernosa in rats with acute arteriogenic erectile dysfunction

IntroductionChronic phosphodiesterase type 5 inhibitor treatment may be useful in reversing erectile dysfunction (ED). However, the mechanisms of this improvement remain unknown.AimThe aim of this article was to determine the mechanisms of the improvement by chronic vardenafil treatment for acute arteriogenic ED in rats.MethodsEight‐week‐old male Wistar‐ST rats were divided into four groups: sham‐operated rats (Control group) and rats with acute arteriogenic ED induced by ligating bilateral internal iliac arteries (Ligation group), subsequently treated with low‐dose (0.4 mg/kg/day; VL group) or high‐dose (4.0 mg/kg/day; VH group) vardenafil for 20 days from 1 week after ligature.Main Outcome MeasuresErectile function was assessed based on changes of intracavernous pressure (ICP) followed by electrostimulation of the cavernous nerves and was evaluated by the area under the curve of ICP/area under the curve of mean arterial pressure (area of ICP/MAP). Transforming growth factor (TGF)‐β₁, vascular endothelial growth factor‐A, endothelial nitric oxide synthase (eNOS), inducible NOS, and neuronal NOS mRNA expression levels in penile corpus cavernosum were determined by real‐time PCR. Western blotting for TGF‐β₁ protein levels and Masson trichrome staining of penile tissues were performed in each at group 4 weeks after surgery.ResultsIn the VH group, area of ICP/MAP was significantly improved when compared with the Ligation group (P < 0.01). The smooth muscle (SM)/collagen ratio in the VH group was significantly higher than in the Ligation group (P < 0.05), and was comparable with that in the Control group. TGF‐β₁ mRNA and protein levels in the VH group were significantly lower when compared with the Ligation group (P < 0.05).ConclusionsChronic vardenafil administration ameliorates impairment of penile hemodynamics and maintains normal SM to collagen ratio in cavernous tissues after acute arterial injury in rats. Hotta Y, Hattori M, Kataoka T, Ohno R, Mikumo M, Maeda Y, and Kimura K. Chronic vardenafil treatment improves erectile function via structural maintenance of penile corpora cavernosa in rats with acute arteriogenic erectile dysfunction. J Sex Med 2011;8:705–711.     

Effects of Chronic Vardenafil Treatment Persist after End of Treatment in Rats with Acute Arteriogenic Erectile Dysfunction

IntroductionIn our previous study, chronic vardenafil treatment improved erectile function soon after the end of the treatment in rats with acute arteriogenic erectile dysfunction (ED).AimThe aim of this study is to evaluate whether the effects of chronic vardenafil treatment persist after the end of treatment using rats with acute arteriogenic ED.MethodsRats were randomly divided into three groups: (i) control; (ii) ligation; and (iii) vardenafil + no treatment. Rats in the ligation and vardenafil + no treatment groups underwent ligature of the bilateral internal iliac arteries to induce acute arteriogenic ED and were subsequently treated with vehicle or vardenafil (4.0 mg/kg/day), respectively, for 3 weeks. Subsequently, all rats were kept for a further 2 weeks with no treatment. Rats in the control group underwent sham surgery.Main Outcome MeasuresErectile function was assessed by changes in intracavernous pressure (ICP). Smooth muscle (SM)/collagen ratios in corpus cavernosum were analyzed by Masson trichrome staining. Transforming growth factor‐β₁ (TGF‐β₁) mRNA and protein levels in corpus cavernosum (CC) were, respectively, evaluated by real‐time polymerase chain reaction (PCR) analysis and Western blotting analysis.ResultsICP/mean arterial pressure (MAP) in the ligation group remained significantly lower than that in control group (P < 0.01). Despite no treatment for 2 weeks, ICP/MAP in the var + no treatment group remained significantly higher than that in ligation group (P < 0.05). SM/collagen ratio in the ligation group remained significantly lower when compared with the control group (P < 0.01). The ratio in the var + no treatment group remained significantly higher when compared with the ligation group at 2 weeks after the end of treatment (P < 0.05). TGF‐β₁ mRNA and protein levels did not differ among the groups.ConclusionsThe effects of chronic vardenafil treatment on erectile function and penile structure persist, even after the end of treatment, in acute arteriogenic ED rats. Hotta Y, Ohno R, Kataoka T, Mikumo M, Takahata Y, Ohno M, Maeda Y, and Kimura K. Effects of chronic vardenafil treatment persist after end of treatment in rats with acute arteriogenic erectile dysfunction. J Sex Med 2012;9:1799–1805.     

Exosome Released From Schwann Cells May Be Involved in Microenergy Acoustic Pulse–Associated Cavernous Nerve Regeneration

BackgroundNeurogenic erectile dysfunction (ED) is often refractory to treatment because of insufficient functional nerve recovery after injury or insult. Noninvasive mechano-biological intervention, such as microenergy acoustic pulse (MAP), low-intensity pulsed ultrasound, and low-intensity extracorporeal shockwave treatment, is an optimal approach to stimulate nerve regeneration.AimTo establish a new model in vitro to simulate nerve injury in neurogenic ED and to explore the mechanisms of MAP in vitro.MethodsSprague-Dawley rats were used to isolate Schwann cells (SCs), major pelvic ganglion (MPG), and cavernous nerve with MPG (CN/MPG). SCs were then treated with MAP (0.033 mJ/mm², 1 Hz, 100 pulses), and SC exosomes were isolated. The MPG and CN/MPG were treated with MAP (0.033 mJ/mm², 1 Hz) at different dosages (25, 50, 100, 200, or 300 pulses) or exosomes derived from MAP-treated SCs in vitro.OutcomesNeurite growth from the MPG fragments and CN was photographed and measured. Expression of neurotropic factors (brain-derived neurotrophic factor, nerve growth factor, and neurotrophin-3) was checked.ResultsNeurite outgrowth from MPG and CN/MPG was enhanced by MAP in a dosage response manner, peaking at 100 pulses. MAP promoted SC proliferation, neurotropic factor (brain-derived neurotrophic factor, nerve growth factor, and neurotrophin-3) expression, and exosome secretion. SC-derived exosomes significantly enhanced neurite outgrowth from MPG in vitro.Clinical ImplicationsMAP may have utility in the treatment of neurogenic ED by SC-derived exosomes.Strength & LimitationsWe confirmed that MAP enhances penile nerve regeneration through exsomes. Limitations of this study include that our study did not explore the exact mechanisms of how MAP increases SC exosome secretion nor whether MAP modulates the content of exosomes.ConclusionThis study revealed that neurite outgrowth from MPG was enhanced by MAP and by SC-derived exosomes which were isolated after MAP treatment. Our findings indicate that one mechanism by which MAP induces nerve regeneration is by stimulation of SCs to secrete exosomes.Peng D, Reed-Maldonado AB, Zhou F, et al. Exosome Released From Schwann Cells May Be Involved in Microenergy Acoustic Pulse–Associated Cavernous Nerve Regeneration. J Sex Med 2020;17:1618–1628.     

Multipotent stromal cell therapy for cavernous nerve injury-induced erectile dysfunction

IntroductionErectile dysfunction (ED) following radical prostatectomy (RP) is a result of inadvertent damage to the cavernous nerves that run close to the prostate capsula. The mechanisms behind the development of post‐RP ED are increasingly recognized and include cavernosal fibrosis and cavernosal smooth muscle apoptosis, resulting from cavernous nerve degeneration due to neuropraxia. In recent years, cell‐based therapies have received increasing attention regarding their potential for recovery of erectile function following cavernous nerve injury (CNI). Multipotent stromal cells (MSCs) are an attractive cell source for this application based on their regenerative potential and their clinical applicability.AimTo review available evidence on the efficacy and mechanisms of action of MSC application for the treatment of ED, with an emphasis on ED following CNI.MethodsA nonsystematic review was conducted on the available English literature between 1966 and 2011 on the search engines SciVerse‐sciencedirect, SciVerse‐scopus, Google Scholar, and PubMed.ResultsMSCs from both bone marrow and adipose tissue have shown beneficial effects in a variety of animal models for ED. While MSC application in chronic disease models such as diabetes, aging, and hyperlipidemia may result in cell engraftment and possibly MSC differentiation, this observation has not been made in the acute CNI rat model. In the latter setting, MSC effects seem to be established by cell recruitment toward the major pelvic ganglion and local paracrine interaction with the host neural tissue.Conclusions.While the type of model may influence the mechanisms of action of this MSC‐based therapy, MSCs generally display efficacy in various animal models for ED. Before translation to the clinic is established, various hurdles need to be overcome. Albersen M, Kendirci M, Van der Aa F, Hellstrom WJG, Lue TF, and Spees JL. Multipotent stromal cell therapy for cavernous nerve injury‐induced erectile dysfunction. J Sex Med 2012;9:385–403.     

Effect of BKCa Channel Opener LDD175 on Erectile Function in an In Vivo Diabetic Rat Model

IntroductionThe development of novel therapeutic options is imperative in patients with erectile dysfunction, especially those non-responsive to phosphodiesterase type 5 inhibitors. LDD175, a potent BKCa channel opener, has a relaxation effect on the in vitro cavernosal smooth muscle strip.AimTo investigate the effect of LDD175 on erectile function using in vivo animal disease model.MethodsMale Sprague-Dawley rats were assigned to a normal control group and seven diabetic groups: diabetic control, sildenafil (1 and 5 mg/kg), LDD175 (5 and 10 mg/kg), LDD175 5 mg/kg plus sildenafil 1 mg/kg, and LDD175 10 mg/kg plus tetraethylammonium.Main Outcome MeasuresIntracavernosal pressure (ICP), ratio of ICP to mean arterial pressure (MAP), and the area under curve of ICP/MAP of eight groups were compared using in vivo pelvic nerve stimulation.ResultsThe ICP, ICP/MAP ratio, and area under curve of the ICP/MAP ratio of the normal control rats increased with an increase in electrical field stimulation voltage. All parameters in the diabetic control group were significantly lower than those in the normal control rats, with an electrical field stimulation ranging from 1 to 5 V (P < .05). LDD175 improved the erectile response in diabetic rats in a dose-dependent manner. The combination of sildenafil (1 mg/kg) and LDD175 (5 mg/kg) showed a significant additive effect (P < .05) on the improvement of erectile function compared with sildenafil (1 mg/kg) alone. The enhancement of erectile function by LDD175 was completely blocked by tetraethylammonium.ConclusionThe results showed that the BKCa channel opener LDD175 improved erectile function in an in vivo diabetic rat model. Furthermore, combination therapy of LDD175 and sildenafil had an additive effect on the improvement of erectile function in diabetic rats. LDD175 could be a new candidate for the treatment of erectile dysfunction.     

Apocynin Improves Erectile Function in Diabetic Rats through Regulation of NADPH Oxidase Expression

IntroductionDiabetes is a risk factor for erectile dysfunction (ED). The proposed mechanisms responsible for diabetic ED are associated with an increase in reactive oxygen species (ROS) production, overactivity of RhoA/ROCK signaling pathway and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, as seen in experimental models of diabetic rats.AimThe aim of this study was to investigate whether NADPH oxidase inhibitor apocynin can ameliorate Streptozotocin (STZ)‐induced diabetes‐related ED by reducing the ROS production and inhibiting the activity of RhoA/ROCK signaling pathway.MethodsThe diabetic rats were treated with and without the NADPH oxidase inhibitor apocynin.Main Outcome MeasuresErectile responses were evaluated by determining mean arterial blood pressure (MAP) and intracavernosal pressure (ICP) with electrical stimulation of the cavernous nerve. Levels of mRNA expression were measured by real‐time polymerase chain reaction (RT‐PCR). Levels of protein expression were examined by Western Blot. ROS production was measured by dihydroethidium (DHE) staining and thiobarbituric acid reactive substances assay.ResultsThe ratio of Maximum ICP‐to‐MAP (MaxICP/MAP) was significantly decreased in diabetic ED rats, compared to that of age‐matched control rats (P < 0.05). Apocynin improved erectile function of diabetic rats (P < 0.05). Expression levels of RhoA (cytosol), nNOS and eNOS were reduced, compared to those of control rats (P < 0.05). Apocynin significantly elevated their expression levels in diabetic rats (P < 0.05). Expression levels of ROCK1, RhoA (membrane fraction), p‐MYPT1 and NADPH oxidase subunits p47^phox and p67^phox were increased in diabetic rats when compared to those of control rats (P < 0.05), and it was observed that apocynin significantly reduced their expression levels in diabetic rats (P < 0.05). ROS production was increased in diabetic rats when compared to that of control rats (P < 0.05), the effect of apocynin was a reduction in the ROS production in diabetic rats (P < 0.05).ConclusionNADPH oxidase inhibitor apocynin can ameliorate diabetes‐related ED by reducing the ROS production and inhibiting the activity of RhoA/ROCK signaling pathway. Li M, Zhuan L, Wang T, Rao K, Yang J, Yang J, Quan W, Liu J, and Ye Z. Apocynin improves erectile function in diabetic rats through regulation of NADPH oxidase expression. J Sex Med 2012;9:3041–3050.